This invention relates generally to retaining apparatus and more particularly to apparatus for connecting a core spray line pipe system to an opening in the wall of a vessel in a nuclear reactor.
The boiling water reactor industry has experienced extensive cracking of internal reactor components. The core spray line piping system is of particular interest as the pipe joints can provide many possible leak paths.
In a typical core spray line, the piping enters the vessel through a safe end above the shroud and immediately goes into a T-head that divides the flow into two pipes. It will be appreciated that a safe end as used herein refers to a coupling pipe used to create a fluid path between two pipes fabricated of dissimilar metals. The coupling pipe is constructed of a material compatible with the pipe sections to be joined.
Within the core spray piping system, each pipe curves around the interior of the vessel until it reaches a downcomer, with one or more supports along the path. The downcomer extends down to the shroud where it enters through another safe end and terminates in a T-head located in the sparger at the top of the shroud.
There are two pipes per unit that serve four half circle spray spargers in the shroud. In existing systems, the joints are typically welded and subject to cracking, thus creating a leak path.
If cracks are found in the core spray line, it may be more advantageous to replace the cracked pipe than to leave the pipe in place and attempt repairs of the cracks. Removal of the cracked pipes will oftentimes necessitate the removal of the existing joint structure adjacent the T-head that connects the core spray pipe system to the vessel.
Installing a new joint structure similar to the one that is removed will typically involve welding various components together, which may not be desirable since the welding process can increase the possibility of corrosion and cracking. Additionally, welding processes may not be desirable from the standpoint of the time that it will take to complete. Preferably, the pipe replacement process will minimize worker exposure time and the time that the plant may be shutdown for maintenance and repair.
According to one aspect of the invention, apparatus is provided for connecting a pipe system to an opening in a vessel in a nuclear reactor that comprises a vessel fitting adapted for installation on the vessel, the vessel fitting including a first side, a second side, and a passage extending therethrough. The first side is adapted to sealably engage the vessel adjacent the opening, and the second side is adapted to sealably engage the pipe system and position the passage in fluid communication with the pipe system.
A plurality of resilient beams are arranged to extend into the opening and position the passage in at least partial alignment with the opening. Each beam comprises a proximate end adjacent the passage and extends away from the first side to a distal end, and a lock member adapted to lockably engage the vessel when the vessel fitting is installed on the vessel. Thus, when the vessel fitting is in an installed condition on the vessel, the first side forms a substantially leakproof seal with the vessel adjacent the opening, the lock member retains the vessel fitting on the vessel, and the pipe system is in fluid communication with the opening.
According to another aspect of the invention, each lock member is adapted to lockably engage a ledge in the opening.
According to another aspect of the invention, the lock members each have a forward actuator surface adapted to slideably engage the vessel and move the plurality of beams from an unflexed position into a flexed position when the vessel fitting is in a partially installed condition during its installation onto the vessel.
According to another aspect of the invention, each lock member has a rear actuator surface adapted to resiliently bear against the ledge when the vessel fitting is in an installed condition.
According to another aspect of the invention, the lock members are adjacent respective distal ends on the plurality of beams.
According to another aspect of the invention, the second side is adapted to sealably engage at least one pipe fitting in the pipe system.
According to another aspect of the invention, the second side is adapted to sealably engage at least one pipe in the pipe system.
According to another aspect of the invention, the second side is adapted to receive a plurality of fasteners for connecting the vessel fitting to the pipe system.
According to another aspect of the invention, apparatus comprising a vessel fitting and a retainer fitting is provided for connecting a pipe system to an opening in a vessel in a nuclear reactor. The vessel fitting is adapted for installation on the vessel and includes a first surface adapted to sealably engage the vessel adjacent the opening, a second surface, a passage extending therethrough, and a plurality of resilient beams extending away from the first surface that are arranged to extend into the opening and position the passage in at least partial alignment with the opening. Each beam comprises a lock member adapted to lockably engage the vessel when the vessel fitting is installed on the vessel.
The retainer fitting is adapted for installation onto the vessel fitting. It includes a flange with a first side and a second side, a barrel with a near end adjacent the first side and extending to a far end, a pipe fitting portion connected to the second side, and a fluid path extending therethrough.
The barrel is adapted to extend through the passage and bear against the plurality of beams when the retainer fitting is installed in the vessel fitting, with the fluid path in at least partial alignment with the opening. The first side is adapted to sealably engage the second surface, and the pipe fitting portion is adapted to sealably engage the pipe system and position the fluid path in fluid communication with the pipe system.
Thus, when the vessel fitting is in an installed condition on the vessel, and the retainer fitting is in an installed condition on the vessel fitting, the first surface forms a first substantially leakproof seal with the vessel adjacent the opening, the second surface forms a second substantially leakproof seal with the first side, the pipe system is in fluid communication with the opening, and the barrel retains the lock members in lockable engagement against the vessel.
According to another aspect of the invention, the barrel has an external surface with a plurality of slots formed therein, wherein each slot extends from at least about the near end to at least about the far end of the barrel, and wherein the plurality of slots are arranged to slideably engage the plurality of beams.
According to another aspect of the invention, apparatus comprising a vessel fitting and a retainer is provided for connecting a pipe system to an opening in a vessel in a nuclear reactor. The vessel fitting is adapted for installation on the vessel and has a first surface, a second surface, a passage extending therethrough, and a plurality of resilient beams extending away from the first surface. The beams are arranged to extend into the opening and position the passage in at least partial alignment with the opening. Each beam comprises a lock member adapted to lockably engage the vessel when the vessel fitting is installed on the vessel.
The retainer is adapted for installation on the vessel fitting and includes a flange having a first side adapted to sealably engage the second surface and a second side adapted to sealably connect to a pipe fitting in the pipe system, a barrel with a near end adjacent the first side and extending to a far end, and a fluid path extending therethrough. The barrel is adapted to extend through the passage and bear against the plurality of beams when the retainer is installed in the vessel fitting with the fluid path in at least partial alignment with the opening.
Thus, when the vessel fitting is in an installed condition on the vessel, and the retainer is in an installed condition on the vessel fitting, the first surface forms a first substantially leakproof seal with the vessel adjacent the opening, the second surface forms a second substantially leakproof seal with the first side, the pipe system is in fluid communication with the opening, and the barrel retains the lock members in lockable engagement with the vessel.